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LED's with separate power source? Answered

Can I have a circuit which runs from a power supply, this circuit has LED's in it, could I make it so that the LED's are still in this circuit but, they run from a separate power supply to the rest of the circuit? If so, how?

7 Replies

That depends on what you mean by "in the circuit." You could put the LEDs on the far side of a bunch of relays. The LEDs would then require their own power supply, and the relays would be driven from your main circuit to switch the LEDs on or off as required. The relays isolate the wiring, but purists would probably argue that they're all part of the same "circuit."

What I want is a way of having one circuit with switches for stages for stages of ignition. SO I want an LED when an ARM switch is flicked, I would like the power for the LED to come from another source though so not to waste the power needed for ignition. Thanks.

Well, that's much simpler than what you described (providing complete information up front can reduce iterative delays). Just use a double-pole switch. Put the LED on one pole, and your arming circuit on the other pole. Similarly for whatever other switch-indicator LEDs you want.

A double-pole switch has two sets of terminals, usually in parallel on either side of the switch itself. The "middle" terminals are the base of the switch (usually connected to ground, or to whatever is at the "hinge" in your schematic). When the switch is thrown, both parallel sets of leads operate together.

So for your case, you'd use one of the parallel sets of terminals for your actual circuit, and the other parallel set for the LED.

You can't really have "separate power" running through the same wire... well, at least not unless one is AC and the other is a DC offset. (Which is how "phantom power" works on professional sound equipment.)